Windows 10 uses peer to peer software to distribute updates, meaning your computer’s resources will be used to send other Windows users their updates. It’s become common practice for large software companies, but it massively reduces your internet speeds (because some portion of your bandwidth is being used as a seed for other peoples’ downloads). It is active by default, but you can disable it (you will still receive updates) like this:
Start button à Settings
Update & Security
Windows Update à Advanced Options
Choose how updates are delivered:
And Switch from On to Off:
Source: Benjamin Arends (BSC)